Deep inelastic scaling functions for

In the previous chapter we expressed all the measurable scaling functions in terms of the quark distributions or number densities. Notice that there are many more experimental scaling functions than quark nmnber densities u, d, s, u,d,s = s, so that the predictive power is in principle very great. 

It would be naive to imagine that all the relations can be tested experimentally. Electromagnetic deep inelastic scattering experiments are difficult enough, but that analogous experiments can be performed at all 

If good energy resolution is required the tts and Ks are first momentum selected so that the neutrinos are being emitted by particles whose momentum is essentially known. This gives rise to a narrow band beam (NBB). There is clearly a loss of intensity in this selection, but it now 

Thus from a knowledge of we can deduce E, but only up to a twofold ambiguity since we don t know whether its parent was a tt or a AT. The beam is thus diachromatic . Unfortunately, as shown in Fig. 17.2, there is an inherent uncertainty in deducing from the measurement of the interaction position R —one does not know where in the decay tunnel the neutrino was produced. The neutrino energy spectrum of the CERN-Dortmund-Heidelberg-Saclay (CDHS) narrow band beam at CERN is shown in Fig. 17.3. 

For NC reactions one cannot detect the final neutrino at all, so one has to rely entirely on the reconstruction of the hadron shower energy and direction, and of course on the point of interaction. In principle if E, En and pjj are known then E, x, y) are fixed. Since 

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Concisely, what has come to be known as the EMC effect is simply the statement that nucleons bound in nuclear matter behave differently from free nucleons in deep inelastic scattering. More precisely, the nucleon scaling functions appear to have a different x dependence when measured for free nucleons or for nucleons bound in nuclei. The deviation of the nuclear scaling functions from the free nucleon case increases with the atomic number A while remaining qualitatively similar for all nuclei. A broad variety of theoretical explanations have been offered ranging from QCD mechanisms to conventional nuclear physics phenomena. Now, the dust is slowly setting, and it appears possible to take stock of the situation. 

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